Valve, especially a pressure control valve

ABSTRACT

A valve, especially a pressure control valve, includes a housing ( 10 ) with a pump connection (P), an appliance connection (A) and a tank connection (T). A piston ( 16 ) controlled by a magnet armature ( 26 ) is guided inside the housing ( 10 ) of the valve. The vavle is provided with a hydraulic damping device ( 34 ) having a damping chamber ( 36 ) in fluid communication with appliance connection (A) through a throttle ( 38 ). The pump connection (P) or the tank connection (T) is selectively joined to the appliance connection (A) via a connecting line ( 40 ) according to the position of the piston ( 16 ). This valve improves upon known control valves so that the control valve remains stable in terms of behavior, especially with regard to permanent oscilliations.

FIELD OF THE INVENTION

The present invention relates to a valve, a pressure control valve inparticular, with a valve housing having pump, appliance and tankconnections. A valve piston can be driven by a magnetic inductor forguided movement within the valve housing.

BACKGROUND OF THE INVENTION

Conventional proportional pressure control valves are used, among otherthings, as control valves for oil-hydraulic systems to deliver a more orless constant output pressure with variable input pressure. The outputpressure to be controlled is assigned by the current signal delivered bysuitable triggering electronics and acting on an actuating magnet. Theactuating magnet may be designed as a pressure sealed oil bath magnetwith a long service life.

Proportional pressure control valves serving this purpose may bedirectly controlled piston valves of a three-way design, that is, withpressure protection on the output side. They are employed, among otherthings, in oil-hydraulic systems to control couplings, in shifttransmissions for exerting a specific pressure buildup and pressurereduction effect, for remote pressure adjustment, for control ofpressure variation over time and for pilot control of hydraulic valvesand logic elements.

Conventional proportional pressure control valves employed for thesepurposes are characterized by poor stability, especially in the case oflow-viscosity fluid media. They begin to vibrate, something especiallyharmful if the conventional valves are to perform special functions, forexample, in motor vehicle power steering systems, areas relating tosafety engineering, or the like. Generally, susceptibility todisturbances has been found to occur in the natural frequency range ofthe valve. The instabilities arising may result in functional failure ofa valve and the relevant parts of its system.

SUMMARY OF THE INVENTION

Objects of the present invention are to provide improved valves withmore stable behavior, in particular with respect to steady-statevibrations, so that the valve is also well suited for specialappliances.

The valve according to the present invention is provided with ahydraulic damping device having a damping chamber connected by athrottle to the connection of the appliance to convey fluid. Optionally,the pump connection or tank connection communicates with the applianceconnection. In the event of displacement of the valve piston toward thechoke as a result of the magnetic force of a switching magnet, the fluidstored in the damping chamber is displaced toward the applianceconnection by the throttle. The displacement volume flow generates localpressure buildup by the throttle. A force directed against thedeflecting force of the valve piston onto the effective pressure surfaceadjoining the flow restriction point may be determined. Thus, a dampingeffect may be exerted on the entire valve piston. As the valve pistontravels back in the opposite direction, this volume of fluid must flowback away from the appliance connection into the damping space, nowincreasing, again by of the throttle as defined. This flow also resultsin damping of the vibrations which occur.

In a preferred embodiment of the valve of the present invention, thethrottle is in the form of a ring disk which impedes the flow of fluidbetween damping space and appliance connection by a flow restrictionpoint. In one embodiment of the valve of the present invention, the flowrestriction point may be in the form of a through opening inside thering disk. Preferably, however, in an alternative embodiment, the flowrestriction point is at least in part in the form of an annular passageformed between the ring disk and parts of the valve housing surroundingthe ring disk. The latter solution improves damping results and can beapplied cost effectively during manufacture.

In addition, the annular passage can discharge into a connecting duct ofthe ring disk communicating with to the damping space to conduct fluid.The ring disk can be flange-connected to the valve housing at variouspoints, the annular passage being interrupted at the connection points,just as it is by frontal mounting of the annular passage in the interiorof the valve housing. A simple yet functionally reliable connection ofthe throttle to the remaining portion of the valve housing is obtainedin this manner.

In another especially preferred embodiment of the present invention, theconnecting line extends at least in part parallel to the direction ofadvance of the valve piston inside the valve housing. This pistonoptionally makes connection with the tank or with the pump connection.As a result of the connecting line, the functional component proper ofthe valve is separated from the damping component, and, as a result, thefunctional reliability of the valve design is increased.

Other objects, advantages and salient features of the present inventionwill become apparent from the following detailed description, which,taken in conjunction with the annexed drawings, discloses a preferredembodiment of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Referring to the drawings which form a part of this disclosure:

FIG. 1 is a top view, partly in section, of a conventional proportionalpressure control valve;

FIG. 2 is a top view, partly in section, of a valve according to thepresent invention;

FIG. 3 is a front elevational view of the throttle of the valve of FIG.2; and

FIG. 4 is a side elevational view of the throttle of FIG. 3.

DETAILED DESCRIPTION OF THE INVENTION

For better understanding of the valve of the invention, a conventionalproportional pressure control valve is described in detail withreference to FIG. 1.

The conventional valve shown in FIG. 1 includes a valve housing 10 inthe form of a screw-insertion cartridge, also designated as a cartridgevalve. The conventional valve is screwed or threaded into a valvereceptacle 12 with its fluid connections P, T, and A, by way of externalthreading 11. A is the appliance connection. P is the pump connection. Tis the tank connection. The main or valve piston 16 extendslongitudinally inside the valve housing 10, and is suitably hardened andground. A magnet system 20, for electric actuation of the piston,includes a circuit box 22 and a controllable magneto inductor 26introduced into a magnetic coil 24. The magneto inductor 26 is connectedto the valve piston 16 by a tappet-like actuating element 28. The frontend of element 28 rests on a resetting or pressure spring 32,specifically, in the area of the appliance connection A. The other freeend of the pressure spring 32 is in contact with a frontal inner recessin valve housing 10.

In the initial position, in which no current flows and the magnetoinductor 26 has not been actuated, the valve is closed on the input sideby the pump connection P. Also, on the output side, connection Acommunicates with the tank connection T to conduct fluid. For thispurpose the valve piston 16 has on its external circumference, at aprescribed distance, an annular recess 54. If a current signal is nowapplied to the magnet system 20 by the circuit box 22, the magnetoinductor 26 presses against the valve piston 16 with a forcecorresponding to the level of the control current. As a result, thecontrol piston 16 is forced downward against the reset spring 32 and thefluid or oil flows from the pump connection P to the applianceconnection A. If a consumer appliance device, such as a hydrauliccylinder or the like, is connected to the appliance connection A, apressure builds up at the connection A which acts on the end surface ofthe control piston and generates a force opposite the magnetic force ofthe magnet system 20 to force the valve or control piston upward again.As a result, the inflow of the pump connection P to the applianceconnection A is reduced until the pressure of the magnetic force appliedto the appliance connection, and thus, the pressure value assigned bythe current signal are again equal. If the consumer device requires nomore pressurized fluid, for example, because the hydraulic cylinder hasreached its throw limit, the valve piston 16 moves upward again andseals the pump connection P. If the output pressure drops, as a resultof relief of pressure on the consumer device, below the prescribedpressure value, the magneto inductor 26 presses the valve piston 16 backdownward and the control process may begin again. The maximum outputpressure which may be reached, also designated as pressure stage, isestablished by the magnetic force.

One possible method of output pressure protection at the directlycontrolled piston valve from appliance connection A to tank connection Tis executed as follows. If the pressure at the appliance connection Aincreases beyond the prescribed pressure, the valve piston is displacedupward with the magneto inductor 26 until the connection of applianceconnection A to the tank connection T is opened. The pressure on theappliance connection A is consequently limited. In the event ofinterruption of the control current, the valve piston 16 is moved upwardby the pressure on connection A and the reset spring 32. As a result,the appliance connection A is again connected to the tank connection Tand the pressure on the appliance connection A drops to the tankpressure level.

The proportional pressure control valve used for this purpose ischaracterized by poor stability, in particular when low-viscosity mediaare employed. In theory, harmful vibrations of the valve around the areaof the valve seat 14 are possible.

To counteract this harmful vibrational behavior, as is to be seen inFIGS. 2 to 4, the valve of the present invention has a hydraulic dampingdevice 34. To the extent that the conventional valve elements describedabove are also used in the valve of the present invention, such valveelements are identified by the same reference number. The samedescription also applies to such valve elements in the disclosedembodiment of the present invention as well. Such elements are explainedonly to the extent that the embodiment of the present invention differsfrom that of the conventional valve previously described.

The damping device 34 is provided with a damping space 36 communicatingwith the appliance connection A by a throttle 38 so as to conduct fluid,and being filled with fluid. Optionally, the pump connection P or thetank connection tank connection T communicates with the applianceconnection A through a connecting line 40, as a function of the positionof the valve piston 16. In the switching position illustrated in FIG. 2,the pump connection P is separated from the appliance connection A.However, pump connection P communicates at least to some extent with thetank connection T by way of the valve piston 16.

The throttle 38 is in the form of a ring disk 42, as is shown in greaterdetail in FIGS. 3 and 4. The ring disk 42 impedes flow of fluid in bothfluid directions between damping space 36 and appliance connection A bya throttle point 44. The throttle point 44 results from the ring disk 42having a clearance of about 55 to 70 μm relative to the intake opening46 in the valve housing 10. The ring disk 42 is otherwise sealed offfrom the appliance connection A. The throttle point could also be in theform of a through opening 47, preferably in the center of the of thering disk 42. For production engineering reasons alone, manufacture ofthe mounting between ring disk 42 and intake opening 46 of the valvebody 10 is simpler to accomplish and so more cost effective.

As seen especially from FIGS. 3 and 4, the ring disk 42 has on its innerside facing the damping space 36 a grooved connecting channel 48. Theconnecting channel 48 may be produced cost effectively, if, inmanufacture of the ring disk 42, a through opening later forming thesemicircular ring channel as connecting channel 48 is made beforetapping of the turned component involved. The connecting channel 48discharges outward on both sides of the ring disk 42. For the purpose ofuse of the valve illustrated in FIG. 2, recesses 50 are made in theexternal circumference on the valve housing 10, to be received in asuitable valve recess 12 (not shown). The recesses receive sealingmeans, especially sealing rings, to ensure sealing of the interior ofthe valve from the environment.

The ring disk 42 is hinge-connected or connected at various points 49 tothe valve housing 10. The fluid-conducting annular gap is interrupted atthe hinge connecting points 49, and by frontal mounting of the ring disk42 on the interior of the valve housing 10 in the form of the intakeopening 46. For the purpose of reliable hinge connection and dependableretention of the ring disk 42 inside the valve housing 10, hingeconnecting points are provided at angles of 90°. At this point, theintake opening 46 narrows at various locations and the cylindrical valvereceptacle 52, which faces the appliance connection or consumerconnection A on the free end of the valve, is correspondingly narrowedat these locations. Up to the four points of application, however, flowof fluid between the appliance connection A and the damping space 36 isnot impeded. Since the ring disk 42 rests frontally against the valvehousing, subsequent flow of fluid into the damping space 36 takes placethrough the connecting channel 48, which both discharges into thedamping space 36 and is connected so as to conduct fluid by way of itsfrontal surfaces to the throttling ring gap.

As is also to be seen from FIG. 2, the connecting line 40 is mounted toextend in part parallel to the direction of travel of the valve piston16 inside the valve housing 10. The piston optionally communicates withthe tank connection T or the pump connection P. The connecting line 40extending parallel to the direction of displacement of the valve piston16 inside the valve housing discharges at one of its free ends into theappliance connection A. At its other free end, line 40 discharges into atie line 56 which discharges into the annular recess 54 in everydisplacement position of the valve piston 16. The tie line 56 is sealedoff from the outside by a sealing ball 58. Like the pump connection P,the tank connection T is mounted transversely to the longitudinaldirection of the valve piston 16. A pressure equalization line 60discharges at one end into tank connection T. The other free end ofpressure equalization line 60 discharges into a pressure space 62penetrated by the actuating component 28 of the magneto inductor 26. Inthis area, magneto inductor 26 comes to rest against the valve piston16.

The tank connection T and the pump connection P are separated from eachother for fluid conduction or communication by a central valve pistoncomponent 64 having the annular recess 54. Depending on the state of thesystem, and thus depending on the displaced position of the valve piston16 and of the central valve piston component 64, a fluid conductingconnection or fluid communication is established between the applianceconnection A and the tank connection T or between the applianceconnection A and the pump connection P. Covering of the annular recess54 with the pertinent connection P or T is effected for thefluid-conducting connection in question. Connections P and T otherwisedischarge into a ringshaped narrowing 66 inside the valve piston 16.These connections are separated by the central valve piston component64.

Other piston components 68 each have conventional sealing means to sealthe pertinent narrowing 66 in both directions. For the sake of betterunderstanding of the valve of the present invention, this valve will nowbe discussed in greater detail on the basis of the function of thevalve.

When the valve or control piston 16 is displaced in the positive, X,direction, that is, toward the ring disk 42, by the magnetic force ofthe magnetic system 20, the volume of fluid present inside the dampingspace 36 is forced from this point in the direction of the applianceconnection A, through the throttle 38 in the form of an annular gap 38between valve housing 10 and ring disk 42. This flow volume displacedthrough the ring gap generates a local pressure buildup. A damping forceon the effective pressure surface of the piston 16 may be detected. Aforce directed against the displacing force of the valve piston 16 thenexerts a damping effect over the entire axis of the valve. On any returnof the valve piston 16 in the opposite, negative, X direction, thisvolume of fluid must now flow back again into the now expanding dampingspace 36 through the ring gap defined as throttle 38. This flow againexerts an inhibiting effect on the valve piston 16. On the basis of thisinhibiting effect produced by the throttle 38, a pressure control valvemarked by high stability toward steady-state vibrations is thusdeveloped at low cost by simple and cost-effective productionengineering means, since inhibition of valve piston movement is createdby the throttle 38 and the damping space 36. Since instabilityconditions associated with the valve may be counteracted in this way,breakdowns during operation are prevented.

The damping space 36 is a component of a central channel extending alongthe longitudinal axis of the valve housing 10. The damping space 36 isbounded on one of its sides by one piston component 68 and on the otherside by the throttle 38. Both the throttle 38 and the damping space 36are adjacent to the appliance connection A on the free, frontal, end ofthe valve housing 10. In addition, the free end of the connecting line40, which extends parallel to the central channel, discharges into theopen at the frontal termination or end of the valve housing 10.

An especially compact structure is thus achieved for the valve, onewhich performs its function with only one throttle point. In addition,the damping is equalized directly as a result of the effect exerted onthe frontal, free, end of the lower piston component 68. The dampingspace 36 is additionally characterized by the fact that this space,except for the throttle 38, is more or less closed, in particular by wayof the sealing device of piston components 68 in the direction of thenarrowing 66 toward the pump connection P.

While one embodiment has been chosen to illustrate the invention, itwill be understood by those skilled in the art that various changes andmodifications can be made therein without departing from the scope ofthe invention as defined in the appended claims.

What is claimed is:
 1. A pressure control valve, comprising: a valvehousing having a pump connection, an appliance connection and a tankconnection; a valve piston movably mounted in said valve housing betweena first position connecting said pump connection and said applianceconnection in fluid communication and a second position connecting saidtank connection with said appliance connection in fluid communication; amagneto inductor located in said housing and coupled to said valvepiston to control movement and positioning thereof; and a hydraulicdampening device mounted in said housing having a dampening space influid communication with said appliance connection through a throttle,said throttle including a ring disk with a throttle point impeding fluidflow between said dampening space and said appliance connection andincluding an annular passage between said ring disk and adjacent partsof said valve housing surrounding said ring disk, said ring disk havinghinge connecting points for connection to said valve housing, saidannular passage being interrupted by said hinge connecting points and byapplication of a front of the ring disk to an interior of said valvehousing.
 2. A pressure control valve according to claim 1 wherein saidthrottling point has at least one through opening inside said ring disk.3. A pressure control valve according to claim 1 wherein said annularpassage discharges into a connecting channel in said ring disk, saidconnecting channel being in fluid communication with said dampeningspace.
 4. A pressure control valve according to claim 1 wherein aconnecting line extends in said housing parallel to an axis along whichsaid valve piston moves; and said valve piston comprises an annularrecess connecting said pump connection and said appliance connection insaid first position and connecting said tank connection and saidappliance connecting said second position, selectively.
 5. A pressurecontrol valve according to claim 1 wherein said tank connection is influid communication through a pressure equalization line with a pressurespace in said housing, said pressure space receiving an actuatingcomponent of said magneto inductor.
 6. A pressure control valveaccording to claim 5 wherein an energy accumulator engages saidactuating element and said valve housing, and biases said actuatingelement against a magnetic force of said magneto inductor.
 7. A pressurecontrol valve according to claim 1 wherein said valve housing comprisesan external thread for mounting said housing in a valve receptacle; andsaid valve housing receives part of a proportional magnet for drivingsaid magneto inductor.